Researchers say that professional cyclists may wish to consider freezing their sperm before embarking on their careers. Sperm quality drops dramatically with rigorous training.
A study of top triathletes found those who cover more than 186 miles a week on their bikes have less than 4 percent normal looking sperm. At such levels, men would have significant fertility problems.
Fifteen triathletes were asked not to have sex for three days before giving a sperm sample. When the results were compared with their training routines, only cycling, and not swimming or running, was linked with sperm quality.